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Artificial muscle does the heavy lifting for soft robots


This flexible artificial muscle can lift more than a thousand times its own weight, writes Andrew Masterson.


Skeleton with an artificial bicep.
Skeleton with an artificial bicep.
Aslan Miriyev / Columbia Engineering
Engineers at Columbia University in New York, US, have created a robotic tissue that can function as an artificial muscle capable of lifting more than one thousand times its own weight.

The 3D-printed material, made from silicone rubber suffused with micro-bubbles containing ethanol, is being hailed as a significant advance in the hot-button field of “soft robotics”.

Soft robotics focuses on the adaptation of flexible, even fragile, materials such as paper, textiles and rubber for use in artificial intelligence or machine learning applications.

As soon as current technical challenges are overcome, soft and malleable robots are likely to play ever-increasing roles in areas such as prosthetics, aged care, and surgery. Around the world there are several high-level facilities dedicated to soft robotics research, including Harvard’s Biodesign Lab in the US and the ARC Centre of Excellence for Electromaterials Science in Australia.

One of the most stubborn technical difficulties associated with the field has been the seemingly intractable need to connect soft robotic tissues to a power source. Previously constructed muscle tissues, for instance, have required external powered compressors to provide either hydraulic or pneumatic pressure to make to flex and contract.

The Columbia team, led by Hod Lipson, has found a way to eliminate this problem almost entirely.

Its silicone-ethanol matrix demonstrates an intrinsic expansion ability, with the tissue able to enlarge by 900% without the use of external compression. The unit is powered by an eight-volt current running through a single thin wire, and maximum expansion is achieved by heating it to 80 degrees Celsius.

Because it is 3D printed, the tissue can be constructed to almost any size and is thus suited to a wide variety of applications. Fabrication is easy, and costs – especially on higher volumes – are low.

“Our soft functional material may serve as robust soft muscle, possibly revolutionising the way that soft robotic solutions are engineered today,” says co-author Aslan Miriyev.

The artificial muscle contracts under an electric current.
The artificial muscle expands under an electric current.
Aslan Miriyev / Columbia Engineering
“It can push, pull, bend, twist, and lift weight. It’s the closest artificial material equivalent we have to a natural muscle.”

The team’s research is published in the journal Nature Communications.

Lipson and his colleagues are now working on refining the new tissue. They aim to incorporate conductive materials to eliminate the need for the connecting wire, and to extend its usable life.

After that, they say, they will combine it with an artificial intelligence system that will learn to control it by responding to immediate stimuli, prompting, they hope, “natural” movement.

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Andrew Masterson is news editor of Cosmos.
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